Jet engines for aircraft

ABSTRACT

A thrust reversal system for an aircraft jet engine comprising a pair of thrust reverser buckets movable between a stowed and a deployed position, an air motor operable under pilot&#39;&#39;s control for imparting movement to the buckets and mechanism for automatically decelerating the air motor as the buckets approach both the stowed and the deployed positions.

[15] 3,655,134 [451 Apr. 11, 1972 United States Patent Greenland et al.

XX 70 n 5 6W H 9 3" 2m n t d mm 6 HF 00 77 99 ll 02 ll 55 75 2O 35 33[54] JET ENGINES FOR AIRCRAFT [72] Inventors: Leonard Sidney Greenland;Charles Philip Smith; David Marshall, all of Wolverhampton, EnglandPrimary ExaminerM. Henson Wood, Jr. Assistant Examiner-Michael Y. MarAttorney-J5. T. Le Gates [73] Assignee: H. M. Hobson Limited, London,England [22] Filed: Nov. 23, 1970 [21] Appl. No.: 91,859

ABSTRACT A thrust reversal system for an aircraft jet engine comprisinga 12 Claims, 8 Drawing Figures [56] References Cited UNITED STATESPATENTS 3,419,218 12/1968 Campbellet Patented April 11, 1972 8Sheets-Sheet 1 Patented April 11, 1972 8 Sheets-Sheet 2 ll 21 r 8Sheets-Sheet 5 aEEmE Patented A ril 11, 1972 Patented April 11, 1972 8Sheets-Sheet 5 EEzE n NE E Patented April 11, 1972 I 3,655,134

8 Sheets-Sheet 6 Patented A ril 11, 1972 8 Shets-Sheec 7 Patented April11, 1972 3,655,134

' 8 Sheets-Sheet 8 JET ENGINES FOR AIRCRAFT This invention provides athrust control system for an aircraft jet engine, comprising a pair ofthrust reverser buckets movable between a stowed and a deployedposition, an air motor operable under pilots control for impartingmovement to the buckets and mechanism for automatically decelerating theair motor as the buckets approach both the stowed and the deployedpositions.

In one preferred embodiment of the invention a snubber valve and a brakeare provided for causing deceleration of the motor as the bucketsapproach the fully closed deployed position and the stowed position.Alternatively the system may include position feedback to an electricalcontrol valve of the air motor or to the snubber valve. In such casesthe snubber valve and/or the brake may be omitted.

Certain embodiments of thrust reversal system according to the inventionwill now be described in more detail, by way of example, with referenceto the accompanying drawings, in which FIG. 1 is a perspective viewshowing the thrust reverser buckets and their operating linkages,

FIG. 2 is a sectional view illustrating the operation of one of thethrust reverse actuators,

FIG. 3 is a diagram illustrating one form of control unit for thebuckets,

FIG. 4 is a sectional view showing details of the combined shut-off andpressure regulating valve shown in FIG. 3, and

FIGS. 6 8 are diagrams showing alternative forms of control unit. Likereference numerals indicate like parts throughout the Figures.

As shown in FIG. 1, the system includes a pair of thrust reverserbuckets 10, mounted on links 11 pivoted to fixed brackets 12 mounted inthe tail pipe of a jet engine (not shown). The buckets are movable byactuators l3 operated by an air motor 14 from a stowed position shown infull lines to a deployed position shown in chain-dotted lines in whichthey are tightly closed together. The actuators 13 are interconnected byflexible shafts 15 (FIG.2) encased in tubes 16 and they are driven fromthe motor 14 by flexible shafts 17 enclosed in tubes 18.

As shown in FIG. 2, each actuator 13 includes a drive shaft 19, fixed atits opposite ends to the flexible shafts 17, 15 and driving a pair ofscrew shafts 20 through spur reducing gears 21, 22 and bevel gearing 23,24.

The rotation of each shaft 20 causes a recirculating ballnut 25 to movealong the screw on the shaft, the torque reaction of each nut beingtaken by the other nut through a connecting beam 26. As shown in FIG. 1,the ballnuts 25 are connected to the links 11 by links 27. Carbon wipers28 and 29 inserted in each nut 25 are used to keep dirt off therecirculating balls 30 and ice chippers 31 and 32 are provided at eachend of the nut. Thrust races 33 and 34 transmit the end loads from theballnuts back to the gearbox structure. Micro-switches 35 and 36 operateat each end of the travel to indicate the position of the buckets to thepilot. I

The motor 14, which is supplied with operating air under pressure fromthe compressor of the engine through an inlet 37 (FIG. 3) under controlof a combined shut-off and pressure regulator valve 38, is provided witha torque failure indicator 39 and, in addition to driving the actuators13, drives through worm and worm wheel gearing 40, a cam shaft 41A showndiagrammatically in FIG. 3 and driving cams 41, 42 43 and 44 whichoperate as explained later.

' As shown in FIG. 4, the valve 38, which contains a valve plunger 45urged to the right to a closed position by a spring 46, is controlled bya solenoid 47. The solenoid is energized only upon closure of twomicro-switches, not shown, in series. One of these switches is closed bymovement of a pilots lever to a deploy position to select reverse thrustand the other switch is closed when the undercarriage of the aircraftsenses ground contact. When the solenoid is de-energized the valve 38 isclosed but it opens upon energization of the solenoid as will now bedescribed.

Energization of the solenoid 47 depresses a piston 48 to shift poppetvalves 49, 50 loaded by springs 51, 52 from shutoff positions to thepositions shown in FIG. 4. A backward facing pressure sensor 53 thentransmits inlet pressure via the valve 49 to a pilot regulator valve 54.The pressure downstream of the valve 54 is fed to a chamber 55 via adamping restrictor 56 and a passage 57. A piston 58 on a spindle 59 isaccordingly moved to the right to the position shown causing the spindle59 to seal the vent connection 60, and the chamber 61 to the right ofthe piston 58 being ported to atmosphere via a passage 61A, the poppetvalve 49 and a vent 62. Downstream pressure is fed into a chamber 63through the open end 64 of a cavity in the spindle 59 from a sensingpoint The force balance on the main valve 45 is made up of two pressurecomponents and a small spring closing force exerted by the spring 46.Downstream pressure, applied to the chamber 63, produces a valve closingforce. This is opposed by the reference pressure in the chamber 55maintained by the pilot regulator valve 54.

As the solenoid 47 is de-energized in this condition the spring-loadedpoppet valves 49, 50 move across to the shutoff position. The chamber 61is then exposed to inlet pressure from the sensor 53 via the poppetvalve 50 and the passage 61A. This causes the piston 58 and the spindle59 to move to the left to close the open end 64 of the spindle, at thesame time opening the vent connection 60 to exhaust the systemdownstream of the regulating valve. Simultaneously pressure to the pilotregulator valve 51 is cut off by the poppet valve 49 and the chamber 55exhausts to atmosphere via the passages 57 and 66 and poppet valve 49,inlet pressure leaks into the chamber 63 past carbon piston rings 67 andassists the spring 46 to close the main valve 45. The spring 46 ensuresthat the valve is closed when the supply pressure is zero.

Movement of the pilots lever to the deploy position not only opens thevalve 38 to pass air at a pressure regulated by the valve along apassage 68 but also shifts a selector valve 69 to the left from theposition shown in FIG. 3, to allow air under pressure to flow from thepassage 68 through passages 70, 71 to a chamber 72 of a reverser bucketlock 73. This causes a piston 74 to move to the left against a spring 75to withdraw a locking peg 76 from a recess 77 in a cam 78 attached toone of the buckets 10. Movement to the left of the piston 74 also allowspressure air to flow through a passage 79 to a chamber 80, so moving apiston 81 to the left against a spring 82. The piston 81 is connected toa directional control valve 83 and to a valve actuator 84. The movementof the piston shifts the valve 83 from the position shown in full linesto that shown in chain-dotted lines so admitting pressure air to apassage 83 leading to the air motor 14. The motor cannot, however, startimmediately because the passage 86 connecting the motor to an exhaustoutlet 87 is initially closed by a snubber valve 88 and a disc brake 89is initially applied to one of the motor shafts.

In the position of the actuator 84 shown in FIG. 3 it holds an interlockvalve 90 open against the action of its spring 91 and allows a companioninterlock valve 92 to close under the action of its spring 93. Airadmitted through a line 94, containing a restrictor 95 and provided witha relief valve 96, to a chamber 97 and to a chamber 98 is vented toexhaust by dump valves 99, 100. Movement of the actuator 84 to the leftallows the valve 90 to close and opens the valve 92. Closure of thevalve 90 closes air bleed paths to exhaust through restrictors 101, 101Aand vent valves 102, 103 which are at this time held open by the cams43, 44 against the action of springs 104, 105. The pressure in passages106, 107 leading to the dump valves 99, accordingly rises, causing thedump valves to close and the pressure in the chambers 97, 98 to rise.Accordingly a piston 108 is moved to the left against the action of aspring 109 to open the snubber valve 88 and a piston 110 is moved to theleft against the action of a spring 111 to take off the brake 89.

The air motor 14 hen drives the buckets to the deploy position, thespeed of operation being limited by a speed control valve 112. The valve112 includes a diaphragm 113, loaded by a spring 114 and subject at itsopposite sides to static and dynamic pressure applied to it by pressurepickoffs 115, 116 in the inlet passage 68. If the dynamic pressureexceeds a limiting value the diaphragm 1 13 opens a valve 1 17 to bleedair from a line 1 18, reduce the pressure in the chamber 97 and causethe snubber valve 88 to reduce the speed of the motor 14 by partialsnubbing of the exhaust outlet 87.

As the buckets approach the deploy position the cam 41 opens a ventvalve 119 to permit an air bleed to exhaust via the open interlock valve92. Pressure in the passage 106 falls due to the bleed across therestrictor 101 and the dump valve 99 accordingly opens to spill air fromthe chamber 97 causing the snubber valve 88 to close the exhaust outlet87. A reverse torque is produced at the motor shaft due to the build-upof air pressure in the blocked exhaust passage and rapid deceleration ofthe motor occurs.

At a later stage in the deceleration the cam 42 opens a vent valve 120to permit an air bleed to exhaust via the interlock valve 92 from thepassage 107 and the dump valve 100 opens to spill air from the chamber98, causing the brake 89 to be applied. Limit stops are fitted at eitherend of the travel of the reverser buckets and the timing of the cams issuch that the output speed is low as the buckets reach the stops.

A similar sequence of operations occurs when the pilots lever is removedto select return of the buckets to the stowed position. This movementde-energizes the solenoid 47 in the regulating valve 38 but this valveis maintained open by admission of air under pressure through an inlet121 (FIGA) to the upper surface of the piston 48, this air being derivedfrom a passage 122 (FIG.3) which is maintained open by an annulus 123 onthe bucket lock plunger 76 until this plunger is able to re-engage therecess 77.

The pilots lever also moves the selector valve 69 to stow positionshown, in which the chamber 72 of the bucket lock is connected toexhaust and air under pressure is applied through a line 124 to the lefthand side of the piston 81. The bucket lock piston 74 then moves towardsthe stow position, under the influence of its return spring 75, untilmovement is arrested by abutment of the locking peg 76 abutting againsta cam face 78. This movement is sufficient to connect the chamber 80 toan exhaust outlet 125 via the passage 79 and chamber 150. The piston 81therefore moves the directional control valve 83 to the stow positionshown in full lines, admitting air at regulated pressure to the airmotor 14 via the passage 86, and connecting the passage 85 to thesnubber valve 88. As the valve 83 moves to the stow position, theactuator 8 allows the interlock valve 92 to close thus blocking the airbleed paths to exhaust across the vent valves 119 and 120 and therestrictors 101 and 101A. The pressure in the passages 106 and 107 risescausing the dump valves 99 and 100 to close. The disc brake 89 istherefore disengaged and the snubber valve 88 is fully opened.

The air motor 14 then drives the buckets towards the stow position. Asthis position is approached the snubber valve closing sequence isinitiated by the cam 43 opening the vent valve 102 and subsequently thedisc brake operating sequence is initiated by the cam 44 opening thevent valve 103. As the buckets reach the limit stops the locking peg 76engages the recess 77 ensuring that the buckets remain securely lockedin the stowed position. At the same time a valve land 126 on the bucketlock shuts off the supply pressure in the passage 122, causing theregulating valve 38 to close.

The directional control valve 83 is locked in its alternative positionsby engagement of a plunger 127 with alternative recesses in the valveactuating linkage, one of which is indicated at 128. The plunger 127 isnormally retracted by a spring 129 but is moved to the locking positionby pressure applied to a diaphragm 130 through a passage 131 when thebrake 89 is disengaged.

In the system just described a cam causes the snubber valve 88 to closeas the buckets approach the deployed or stowed position to deceleratethe motor and at a later stage another cam applies the brake 89. Certainmodified control systems will now be described which provide positionfeedback to the directional control valve, the snubber valve beingsometimes omitted, or to the snubber valve, and in which the brake is insome cases dispensed with.

In the system shown in FIG. 5 the solenoid 47 of the pressure regulatingvalve 38 is energized as before when the pilots lever is moved to deployprovided ground contact has been made, so causing the valve 38 to open.Movement of the pilots lever to deploy moves the selector valve 69 tothe left to supply pressurized air to the right hand side of the bucketlock piston 74. When this pressure has moved the piston 74 to the leftto retract the plunger 76 and open a valve 132 in the line 122, thepressurized air passes through a passage 133 to an actuator piston 134for actuating the directional control valve 83.

The actuator piston 134 is accordingly moved down to cause adifferential lever 135 to shift a link 136 and move the valve 83downwardly to supply air to the air motor 14, which accordingly rotatesto move the buckets to the deployed position. Rotation of the motorcauses the differential lever 135 to provide feedback to the valve 83 inthe direction to close it, the feedback drive being taken via areduction gear 137 and a recirculating ball screw 138. The velocity ofthe piston 134 is controlled by restrictors 139 and 140.

As the deployed position is approached, the piston 134 contacts adashpot 141 and gradually slows down so that it contacts its end stopwith minimal velocity. As the piston 134 decelerates, the motor 14 willtend to run on until it in turn is decelerated when the output issufficiently out of phase with the input to have reversed the porting ofthe valve 83 so that the motor acts as a brake. The travel of the piston134 is such that the valve 83 is sufficiently open when the buckets areclosed to ensure that the closing torque is always present.

The stowing action is the reverse of the above. The shut-off valve 38 isheld open after the solenoid 47 has been de-energized by pressurethrough the connection 122 and the valve 132. It is thus kept open untilthe buckets have reached the position in which the lock 76 re-engages. Arelief valve 147 protects the buckets from excessive loads by limitingthe pressure drop across the motor 14.

FIG. 6 shows a similar system but with a different feedback arrangementin which the position of the fulcrum 142 of a lever 143 interconnectingthe piston 134 and the directional control valve 83 is progressivelyadjusted by gearing 144 driven by the motor 14. The system includes thesnubber valve 88 connected to the lever 143 and therefore caused toassume a position depending on the extent of travel of the buckets.

FIG. 7 shows a further system in which position feedback similar to thatof FIG. 5 is applied both to the actuator piston 134 of the directionalcontrol valve 83 and to snubber vent valves 102, 119 which operatetowards the end of the movement of the buckets to vent the pressureacting on the upper end of the piston 108 of a snubber valve actuatorand cause it to be moved by the spring 109 to close a snubber valve 88.As the piston 134 moves to operate the directional control valve 83 itshifts an actuator 146 to allow the vent valve 102 to close, so causingthe piston 108 to open the snubber valve 88. The other vent valve 119 isopened through the agency of the feedback mechanism 145 and the actuator146 as the deploy position is neared to cause the snubber valve 88 toclose again. A maximum speed control valve 112 controlled by flyweights148 driven by the motor 14, opens a valve 117 when necessary to bleedair from the piston 108 and causes partial closure of the snubber valve.

FIG. 8 shows a variant of the system of FIG. 7 providing feedbackcontrolling a disc brake 89, having an actuator piston 110, brake ventvalves 103, 120 interlock valves 90, 92 and a speed control valve 112which operate as described with reference to FIG. 3. The vent valvesinstead of being operated by cams are operated by an actuator 146 linkedto the piston 134 through the agency of the feedback mechanism 145.

What we claim as our invention and desire to secure by Letters Patentis:

1. A thrust reversal system for an aircraft jet engine comprising a pairof thrust reverser buckets movable between a stowed and a deployedposition, an air motor operable under pilots control for impartingmovement to the buckets and mechanism for automatically decelerating theair motor as the buckets approach both the stowed and the deployedpositions.

2. A system as claimed in claim 1, in which the air motor includes asnubber valve and which comprises mechanism operated by the motor forimparting closing movement to the snubber valve when the buckets nearthe end of their travel.

3. A system as claimed in claim 2, which includes a pneumatic servomotor for operating the snubber valve and vent valves controlled by camsoperated by the air motor for venting air from the servo motor near theend of the travel of the buckets.

4. A system as claimed in claim 2, in which the closing movement isimparted to the snubber valve by feedback from the air motor.

5. A system as claimed in claim 1, which comprises a brake for the airmotor and a pneumatic servo motor arranged to apply the brake when thebuckets near the end of their travel.

6. A system as claimed in claim 5, which includes vent valves operatedby the air motor for venting air from the servo motor for the purpose ofapplying the brake.

7. A system as claimed in claim 5, which includes a feedback connectionfrom the air motor which is operative on the servo motor to effectapplication of the brake.

8. A system as claimed in claim 1, which includes a directional controlvalve for the air motor, a pneumatic servo motor for actuating saidvalve and a selector valve operative under pilots control to cause saidservo motor to move the directional control valve in the directioncorresponding to the intended direction of travel of the buckets.

9. A system as claimed in claim 8, which includes a feedback connectionbetween the air motor and the directional control valve.

10. A system as claimed in claim 1, which includes two ball servoactuators operated by the air motor for imparting movement to thebuckets.

11. A system as claimed in claim 1, which includes a pneumaticallyoperated locking plunger for locking the buckets in the stowed positionand a selector valve operable by the pilot to retract the plunger uponselection of movement of the buckets to the deployed position and tourge the plunger towards its locking position on selection of movementof the buckets to the stowed position.

12. A system as claimed in claim 11, which includes a combined shut-offand pressure regulating valve arranged to open under solenoid controlupon selection by the pilot of movement of the buckets to the deployedposition and to be retained open pneumatically under control of apneumatic servo motor controlling the locking plunger until the lockingplunger has returned to locking position upon return of the buckets tothe stowed position.

1. A thrust reversal system for an aircraft jet engine comprising a pair of thrust reverser buckets movable between a stowed and a deployed position, an air motor operable under pilot''s control for imparting movement to the buckets and mechanism for automatically decelerating the air motor as the buckets approach both the stowed and the deployed positions.
 2. A system as claimed in claim 1, in which the air motor includes a snubber valve and which comprises mechanism operated by the motor for imparting closing movement to the snubber valve when the buckets near the end of their travel.
 3. A system as claimed in claim 2, which includes a pneumatic servo motor for operating the snubber valve and vent valves controlled by cams operated by the air motor for venting air from the servo motor near the end of the travel of the buckets.
 4. A system as claimed in claim 2, in which the closing movement is imparted to the snubber valve by feedback from the air motor.
 5. A system as claimed in claim 1, which comprises a brake for the air motor and a pneumatic servo motor arranged to apply the brake when the buckets near the end of their travel.
 6. A system as claimed in claim 5, which includes vent valves operated by the air motor for venting air from the servo motor for the purpose of applying the brake.
 7. A system as claimed in claim 5, which includes a feedback connection from the air motor which is operative on the servo motor to effect application of the brake.
 8. A system as claimed in claim 1, which includes a directional control valve for the air motor, a pneumatic servo motor for actuating said valve and a selector valve operative under pilot''s control to cause said servo motor to move the directional control valve in the direction corresponding to the intended direction of travel of the buckets.
 9. A system as claimed in claim 8, which includes a feedback connection between the air motor and the directional control valve.
 10. A system as claimed in claim 1, which includes two ball servo actuators operatEd by the air motor for imparting movement to the buckets.
 11. A system as claimed in claim 1, which includes a pneumatically operated locking plunger for locking the buckets in the stowed position and a selector valve operable by the pilot to retract the plunger upon selection of movement of the buckets to the deployed position and to urge the plunger towards its locking position on selection of movement of the buckets to the stowed position.
 12. A system as claimed in claim 11, which includes a combined shut-off and pressure regulating valve arranged to open under solenoid control upon selection by the pilot of movement of the buckets to the deployed position and to be retained open pneumatically under control of a pneumatic servo motor controlling the locking plunger until the locking plunger has returned to locking position upon return of the buckets to the stowed position. 